Caption: Hydrogen fuel storage device being held in a gloved hand. This is a metal hydride storage device, which stores hydrogen in the form of a metal hydride. The hydride is usually heated, or passed over a catalyst, to produce hydrogen gas. The process can be reversed to refuel the storage unit. Once released, the hydrogen gas is combined with oxygen in a fuel cell to produce electricity, heat and water. This technology is a clean source of power compared to the pollutant gases produced by the burning of fossil fuels.